I masturbate at least once a day, and while there's some truth to the conditioning thing Ms. Muffintops talks about, that's true of any repeated activity. Eating, movie-watching, working -- anything can condition you if you've got some kind of reward system. It's all individual, is the problem.
For me, the conditioning isn't the problem, I don't think -- it's that if I found myself in an intimate situation again, I think the psychological pressure and nervousness would make functionality difficult. I'm over 40, the hormones no longer flow strongly enough to overwhelm all other opposition. And after all these years being involuntarily celibate, that pressure to perform is going to be fucking intense (pun intended). I don't want to miss my chance, it could be my last opportunity, and that desire is going to fuck up my ability to actually do anything.
So, don't be me, in other words.
But that has nothing to do with masturbation. Everybody's different. There's no physical health risks, your morality is your own business, and psychological difficulties vary widely with the individual. Vague enough for you?